Cranberry capsules not found to reduce asymptomatic bacteriuria in elderly women residing in nursing homes, but insufficient data to assess effect on preventing UTIs

Bacteriuria and pyuria are common in elderly women residing in nursing homes, but symptomatic urinary tract infections (UTIs) occur much less frequently.

A randomized trial investigated the effect of cranberry capsules containing proanthocyanidin on the presence of bacteriuria and pyuria in 185 elderly women residing in nursing homes. Cranberry capsules taken for 1 year were not associated with a reduction in bacteriuria and pyuria or symptomatic UTIs compared to placebo.

These findings suggest that the use of cranberry capsules does not reduce bacteriuria and pyuria in elderly women living in nursing homes. The number of women evaluated in this trial was not sufficient to draw conclusions on the less frequent clinical outcome of symptomatic UTI.

The prevalence of asymptomatic bacteriuria in older women in nursing homes is high with estimations between 25%-50% (Am Fam Physician 2006 Sep 15;74(6):985). However, bacteriuria is not considered a problem as most bacteriuria in this population is not associated with symptoms and often resolves without intervention (J Am Geriatr Soc 1995 Jun;43(6):618). Systematic reviews assessing the efficacy of cranberry products for the prevention of UTIs are limited by significant heterogeneity of the populations in the included trials (Cochrane Database Syst Rev 2012 Oct 17;(10):CD001321, Arch Intern Med 2012 Jul 9;172(13):988). Recently, a randomized trial investigating proanthocyanidin, a substance in cranberries known to inhibit the adherence of P-fimbriated E. coli, was conducted in elderly women in nursing homes. The rationale was that many women in nursing homes with bacteriuria are often treated for UTI based on vague symptoms and prevention of bacteriuria with cranberry capsules might reduce unnecessary antibiotic use. In this trial, 185 women (mean age 86 years) with and without bacteriuria plus pyuria were randomized to 2 cranberry capsules with a total of 72 mg of proanthocyanidin (which is equivalent to the amount found in 20 ounces [590 mL] of cranberry juice) versus 2 placebo capsules once daily for 360 days. Urinalysis for the detection of bacteriuria (≥ 105 colony forming units/mL of 1 or 2 organisms) and pyuria (any number of white blood cells) was performed at 2-month intervals for a period of 1 year. Diagnosis of symptomatic UTI was based on bacteriuria plus symptoms.

At baseline, bacteriuria plus pyuria was present in 28.3% of the women randomized to cranberry capsules and in 34.4% of those receiving placebo (statistical testing not performed). Adjusted analysis (accounting for missing data and covariants) of 723 urine specimens taken throughout the year revealed no significant differences in bacteriuria plus pyuria which was present in 29.1% of specimens from those taking cranberry capsules versus 29% from those taking placebo. Similarly, no significant differences were observed for the secondary outcomes of symptomatic UTI (9.8% versus 9.7% of women), antibiotic administration for suspected UTI, hospitalization, or mortality. Only 65% of the total planned urinary specimens were collected with missing values due to death or incontinence.

The results from this current trial suggest that cranberry products (as represented by proanthocyanidin) do not reduce bacteriuria plus pyuria in elderly women. While these results in and of themselves are not particularly noteworthy, this article was well covered in the news media and was represented as providing evidence that cranberry capsules are not effective for preventing UTIs. From an EBM perspective, the key things to keep in mind are that asymptomatic bacteriuria in an elderly female population is not abnormal and does not require treatment, and that vague symptoms plus bacteriuria are not an indication for antibiotics. It is well known that elderly people may present with atypical symptoms such as confusion or falls, but these are only suggestive of a UTI when there is a clear change from baseline. Finally, with only 10 episodes of symptomatic UTIs in the intervention group and 12 in the control group, the trial was underpowered to detect a difference in this outcome, and, therefore, it was inconclusive on what really matters to the patient.